This invention relates generally to gas turbine engines and more particularly to nozzle locks for circumferentially securing turbine nozzles in such engines.
A gas turbine engine includes a compressor that provides pressurized air to a combustor wherein the air is mixed with fuel and ignited for generating hot combustion gases. These gases flow downstream to one or more turbines that extract energy therefrom to power the compressor and provide useful work such as powering an aircraft in flight. Each turbine stage commonly includes a turbine rotor and a stationary turbine nozzle for channeling combustion gases into the turbine rotor disposed downstream thereof. The turbine rotor includes a plurality of circumferentially spaced apart blades extending radially outwardly from a rotor disk that rotates about the centerline axis of the engine. The nozzle includes a plurality of circumferentially spaced apart vanes radially aligned with the rotor blades. Turbine nozzles are typically segmented around the circumference thereof with each nozzle segment having one or more nozzle vanes disposed between inner and outer bands that define the radial flowpath boundaries for the hot combustion gases flowing through the nozzle.
In a typical mounting arrangement, the outer band of each nozzle segment includes flanges or hooks for coupling the nozzle segment to the inner surface of the engine casing. The inner bands are ordinarily coupled to stationary support structure within the engine. These arrangements provide radial and axial support for the turbine nozzle. During operation, turbine nozzles also generate substantial tangential loads because of the hot gas flow passing therethrough. Gas turbine engines use anti-rotation devices, referred to as nozzle locks, to circumferentially secure the turbine nozzle relative to the engine casing and react the tangential loads.
One known nozzle lock arrangement includes a locking member having two lugs and an integral threaded stud. The locking member is installed from the interior of the engine casing so that the first lug is received in a notch formed in the outer band of one nozzle segment and the second lug is received in a notch formed in the outer band of an adjacent nozzle segment. The threaded stud extends through an opening in the casing and is secured by a nut threaded onto the stud from the exterior of the casing. This nozzle lock arrangement causes the accumulation of nozzle load stress and fastener pre-load stress to occur at the same location, i.e., at the undercut fillet at the base of the threaded stud. This nozzle lock also reacts the tangential load for two nozzle segments. As a result, these nozzle locks can be susceptible to fatigue damage and rupture.
Accordingly, it would be desirable to have a nozzle lock that is less susceptible to fatigue damage and rupture.
The above-mentioned need is met by the present invention, which provides a nozzle lock for a gas turbine engine having an engine casing and at least one nozzle segment disposed inside the engine casing. The nozzle lock includes a thickener pad joined to an outer surface of the engine casing and a locking member disposed in a notch located in the outer band of the nozzle segment. A pin formed on the locking member is press-fit into the casing and the thickener pad.
The present invention and its advantages over the prior art will become apparent upon reading the following detailed description and the appended claims with reference to the accompanying drawings.